ELI5: How Do Bone Marrow Transplants Work/Are Done?

Most "bone marrow transplants" now are usually really stem cell transplants.

There are two basic kinds: allo annd auto.

With an auto, you take a medicine that cause your body to move stem cells from your bone marrow to your blood stream. This is the innovation that has allowed stem cell transplants to mostly replace bone marrow transplants. Then you are hooked up to two needles, one in each are. Blood goes out one and back in the other. In between, the stem cells are separated out. When you have enough, they are frozen.

With an allo, another person does this stem cell donation instead of doing it yourself. The closer their blood is to your own, usually the better. A matched sibling is often your best bet.

Then you are given a heavy dose of chemo to try and kill all the cancer (this procedure is most commonly used for cancer treatment). You get the most your body can stand. It you sicker than a dog and your immune system is destroyed by the chemo. (For multiple myeloma, if you are getting and allo, they give you a reduced level of chemo so that it just weakens rather than destroys your immune system.)

Then you are given the stem cells that were stored previously. This procedure is just like a blood transfusion. These stem cells regrow your immune system. Until this happens, you are very immune compromised and must take precautions to not get sick. Most people end up in the hospital a few times during this process. Some centers do the entire procedure as in patient.

With an auto, you start to recover pretty quickly (about 2 weeks).

An allo is much more dangerous than an auto. With an allo, it takes longer since you have another persons immune system and have to worry about Graft versus Host Disease (GVHD). Your new immune system can think any part of your body is foreign and attack it. This is what GVHD is. Most commonly, it causes nausua and dry eyes, but can effect our lungs or other major organs. You will have to be on anti-rejection drugs, likely for an extended period until your new immune system and your body come to a workable accommodation. Most patients with an allo have some acute GVHD for a while after the procedure. A smaller number have chronic GVHD that lasts long term. GVHD can be a nuisance or very severe. It can be fatal. With Multiple Myeloma, the "reduced intensity" allo has a fatality rate of about 15%. This is, I believe, significantly higher than with other cancers and is why Multiple Myeloma patients have the reduced intensity.

If you have to have a true bone marrow transplant, they have to get the cells from the bone instead of the blood. This also uses a needle, but is more painful, and usually has some sedation.

Not a doctor, so just so you know. The cells involved are known as Hematopoietic stem cells and don't always need to be transplanted via bone marrow. However, the process you're thinking of usually involves a giant needle being inserted into your hip (under local anesthesia) and extracting the marrow from there.

Check out Be The Match and please consider becoming a donor. I'm one, and hope one day I can be lucky enough to save someones life!